The following half-reactions occur in the mercury battery used in calculators. If E°_cell = 1.357 V, calculate the equilibrium constant for the cell reaction at 25°C. (Assume the stoichiometric coefficients in the cell reaction are all equal to 1.) HgO(s) + H₂O(l) + 2e⁻ ⇄ Hg(l) + 2OH⁻(aq)
ZnO(s) + H₂O(l) + 2e⁻ ⇄ Zn(s) + 2OH⁻(aq)

Question

Quizplus · Accepted Answer

The equilibrium constant (K) for the cell reaction can be calculated using the Nernst equation at standard conditions (25°C or 298 K) and the given standard cell potential (E°cell = 1.357 V). The formula to use is: K = 10^(nE°/0.0592), where n is the number of moles of electrons transferred in the balanced equation (n = 2 in this case), and E° is the standard cell potential in volts. Plugging in the values gives K = 10^(2*1.357/0.0592) ≈ 10^45.9, which is closest to 7.5 × 10^45.

The Following Half-Reactions Occur in the Mercury Battery Used in Calculators